The present invention relates to the field of orthopedic surgery, more specifically to methods and apparatus for inserting interlocking screws in intramedullary (IM) nails and for drilling and placing screws in other fractures or when using other implants which do not require IM nails. The method and apparatus are used with C-arm radiation apparatus which emits a beam between an emitter and a receiver at opposite ends of the “C” of the C-arm.
In the first type of surgery, IM nails are primarily used by orthopedic surgeons to fix fractures of the femur, tibia, or humerus, although they can be used to fix fractures in other bones as well. An IM nail is a cylindrical metal rod which includes hollow, open slots near the proximal end and near the distal end, and is designed to be placed down the center of the long femur or tibia bones. The slots are adapted to receive screws. During repair of femur and tibia fractures, an IM nail is first inserted through the center of the bone from the proximal end toward the distal end of the bone. The IM nail used for femur fractures has a proximal slot at an oblique angle and a proximal screw is inserted toward the head of the femur and through the proximal slot.
The IM nail has two distal slots, each aligned at 90° to the length of the nail, adapted to receive distal screws. After the proximal screw is inserted, the distal screws must be inserted by drilling through the distal portion of the femur and the distal slots of the IM nail, and inserting the distal screws.
While the proximal screw is typically placed by use of a guide which attaches to the top of the nail, a similar guide cannot be used to place the distal screws. Because of the distance a guide has to travel from the top of the nail to the bottom of the nail, small amounts of motion in the guide would lead to an inability to line up the guide properly with the distal drill holes. The nail geometry can change slightly as it is inserted due to body temperature and mechanical forces placed on it during insertion, which is another reason guides cannot be used reliably for the distal screws in this type of surgery.
Placing the distal screws close to 90° to the length of the nail is very important since it decreases the friction between the IM nail and the screw and more evenly spreads out the forces which the screw encounters, reducing the risk that the screw will break over time. Such placement also optimizes the prevention of up and down movement of the IM nail in relation to the bone and prevents the nail from rotating.
The current state of the art is to place distal screws by a freehand technique called “perfect circles” with the assistance of an X-ray machine called a C-arm (FIG. 1) which consists of two cylinders, one of which emits an x-ray beam and the other of which captures an image. The C-arm is set up next to the patient and is turned 90° with the patient's leg being placed between the two cylinders in order to get the X-ray machine and beam parallel to the ground and perpendicular to the leg (FIG. 2).
Then the patient's leg is moved manually with the goal of lining up the entry and exit holes in the nail with the x-ray beam. Then an X-ray image is taken. If the entry and exit holes are lined up perfectly, the image of the slot shows one “perfect circle.” If the image shows clear overlap, the leg is readjusted and another image is taken, repeating this process until perfect circles are achieved. Then the surgeon places the tip of the drill in the exact center of the perfect circles.
While keeping the tip of the drill bit in the exact center of the perfect circles, the surgeon visually tries to align the back end of the drill with the imagined plane of the X-ray beam which goes through the leg, between the two cylinders of the C-arm. Then the surgeon drills through the bone, through the exit and entry of a hole in the IM nail. The prior observation of a perfect circle in the X-ray image of the distal IM nail hole proves that the C-arm is perfectly parallel to the hole. By manually aligning the direction of the drill bit with an imaginary line between the C-arm cylinders, the surgeon attempts to drill through the bone and the hole in the IM nail.
In the second type of surgery, a fracture is repaired by drilling a hole on an offset angle to the length of a bone, ideally situated perpendicular to the fracture line that is being fixed. The surgeon then places a screw through the previously drilled hole, ideally at 90 degrees through the line of the fracture.
The methods currently in use are not always successful, resulting, in the case of the first type, in the screw sitting obliquely or even outside the IM nail, either in front of or behind it. In the case of the second type, the surgeon is not always able to place the screw in the exact desired and optimum location, which may lead to suboptimal alignment and compression of the fracture fragments.
There have been many attempted solutions proposed by others, including complicated, sophisticated, and expensive apparatus, but none of those proposed solutions have been widely adopted by orthopedic surgeons. Thus there has been a long-felt need for a lower cost, simple, and highly effective solution to this problem.